Problem: $ { {2} \times \left[\begin{array}{rr}{2} & {4} \\ {-1} & {-2} \\ {4} & {2}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{2}\times{2} & {2}\times{4} \\ {2}\times{-1} & {2}\times{-2} \\ {2}\times{4} & {2}\times{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {8} \\ {-2} & {-4} \\ {8} & {4}\end{array}\right]}$